Investors who hoped that a spike after the market open Tuesday spelled the end of recent pain were sorely disappointed.

The Dow Jones industrial average suffered a 645-point reversal on Tuesday—the largest reversal since the peak of the financial crisis in October 2008. In a CNBC special report Tuesday night, Jim Cramer called it an "uncertain time" for markets but noted that many opportunities still exist, particularly in high dividend yield companies.

As of Tuesday evening, 97 percent of the S&P 500's largest sector had entered correction territory with semiconductor companies Micron Technology and SanDisk leading the way lower. The index as a whole has lost nearly $2 trillion in market cap over the last seven sessions.

"We don't want our clients to panic but we are expecting more volatility," said MaryAnn Bartels, chief investment officer of portfolio solutions at Merrill Lynch, on Tuesday night. "The markets may not have bottomed yet."

She noted that it could take "weeks or months before we actually see a good settling within this market."

Bartels and Scott Minerd, managing partner at Guggenheim Partners, both noted that the volatility does not reflect structural problems in the U.S. Minerd stressed that emerging market issues will continue to weigh on U.S. stocks.

"As long as we have problems in emerging markets, that's going to create headwinds for U.S. stocks," Minerd said Tuesday night, adding that markets are part of the way through a "major correction."

Lightly-traded stock futures for Wednesday implied slightly negative opens for major U.S. averages.